<?php
class Model_Users extends Zend_Db_Table_Abstract
{
    protected $_name = 'users';
    private static $_instance;
    
    public static function getInstance(){
         if(self::$_instance == null){
             return new self;
         }
         return self::$_instance;
    }
    
    public function __clone()
    {
        throw new Exception('Cloning is not allowed', E_USER_ERROR);
    }
}